The functional vessels of human and animal bodies, such as blood vessels and ducts, occasionally weaken or even rupture. For example, the aortic wall can weaken, resulting in an aneurysm.
One surgical intervention for weakened, aneurismal, or ruptured vessels involves the use of an endoluminal prosthesis to provide some or all of the functionality of the original, healthy vessel and/or preserve any remaining vascular integrity by replacing a length of the existing vessel wall that spans the site of vessel failure. Stent grafts for endoluminal deployment are generally formed from a tube of a biocompatible material in combination with one or more stents to maintain a lumen. Stent grafts effectively exclude the defect by sealing both proximally and distally the defect, and shunting blood through its length.
In many cases, however, the damaged or defected portion of the vasculature may include a branch vessel. For example, in the case of the abdominal aorta, there are at least three major branch vessels, including the celiac, mesenteric, and renal arteries, leading to various other body organs. Thus, when the damaged portion of the vessel includes one or more of these branch vessels, some accommodation must be made to ensure that the prosthesis does not block or hinder blood flow through the branch vessel.
Attempts to maintain blood flow to branch vessels have included providing one or more fenestrations or holes in the side wall of the prosthesis. Conventionally, a balloon expandable bare stent is deployed into the renal arteries through the fenestration in the main graft to assure alignment is maintained while the stent-graft is being delivered (e.g., manipulated) and continues to maintain patency post-procedure. The arterial tree is constantly under pulsatile motion due to the flow of blood through the arteries. Thus, the deployed bare metal secondary stent is often under severe and complicated loading conditions which must be borne entirely through the narrow interface presented by fenestrated prosthesis and the bare secondary stent. These conditions may cause deterioration of the secondary stent, and may put the patient at risk of injury. Furthermore, since conventional fenestrated grafts have a fixed interface, there is little room for error when deploying the prosthesis for treatment of the aneurysm. The deployment of the prosthesis has to be extremely precise to assure that the fenestrations are aligned with the branch vessels. If these branch vessels are blocked by the prosthesis, the original blood circulation is impeded, and the patient can suffer. The blockage of any branch vessel is usually associated with unpleasant or even life-threatening symptoms.